Re: [css3-transitions] starting and reversing animations

On Jan 29, 2010, at 9:58 AM, Simon Fraser wrote:

>> Hmmm.  I attempted to explain that in the spec when I wrote:
>> # When the value of an animatable property changes,
>> # implementations must decide what transitions to start based on
>> # the values of the ‘transition-property’, ‘transition-duration’,
>> # ‘transition-timing-function’, and ‘transition-delay’ properties
>> # at the time of the change. Since this specification does not
>> # define what property changes are considered simultaneous,
>> # authors should be aware that changing any of the transition
>> # properties a small amount of time after making a change that
>> # might transition can result in behavior that varies between
>> # implementations, since the changes might be considered
>> # simultaneous in some implementations but not others. 
>> In the new "Starting of Transitions" section.
>> 
>> However, rereading it, I now realize that "at the time of the
>> change" is not clear at all.  What I meant to say is probably "at
>> the time that would be immediately after the change if no
>> transitions had been specified".  Does that make it clearer?
> 
> I don't think this really captures the issue that will most affect
> authors, which is whether the transition properties themselves
> should be considered to come from the current style, or the
> "destination" style.

I thought that was already kind of obvious. If a transition is in a rule for 'hover', it should be triggered when you start to hover. If there is a different transition rule for non-hover, then it is triggered when you leave the hover state. I don't know why anyone would imagine otherwise. The property is called 'transition', not 'transition-when-this-rule-is-about-to-be-no-longer-true'. Once your cursor hovers over the element, the ':hover' rule takes effect, and the 'transition' property in that rule takes effect.

> Perhaps an example in the spec would make this clearer.

It wouldn't hurt.